A novel high performance refrigerant-air heat exchanger employing multiport extruded tubes which have parallel refrigerant mini-channels has recently been developed for heat pump systems. In evaporators, the inequality in heat loads among parallel refrigerant channels causes also inequalities in flow rates of refrigerant. This flow maldistribution induced by unequal heating not only makes it difficult to predict heat exchange performance accurately but also often leads to the deterioration of the refrigerant heat transfer.

In the present study, an experiment was conducted on flow boiling heat transfer of a refrigerant R410A flowing in parallel two mini-channels individually heated by hot water flows. When the parallel channels were heated unequally, the heat transfer rate from the hot water to the refrigerant in the channel with higher degree of wall superheat did not change so much, while that with lower degree of wall superheat remarkably decreased from the equally-heated condition. Consequently, the two-channels-mean heat transfer rate dropped off with expanding the inequality in degree of wall superheat between the channels. The deterioration of the mean heat transfer coefficient under the unequally-heated condition was significant at a high mean flow rate condition which required a large heat transfer rate for evaporation.

最近已经开发出一种新颖的高性能制冷剂-空气热交换器，该热交换器采用具有平行的制冷剂小通道的多端口挤压管，用于热泵系统。在蒸发器中，平行制冷剂通道之间的热负荷不均也会导致制冷剂流量不均。由不均匀加热引起的这种流量分配不均，不仅使准确地预测热交换性能变得困难，而且还常常导致制冷剂传热的恶化。

在本研究中，对制冷剂R410A在两个分别由热水流加热的平行小通道中并行流动的沸腾传热进行了实验。当平行通道不均匀地加热时，壁过热度较高的通道中从热水到制冷剂的传热速率变化不大，而壁温较低的通道的热传递速率从均热状态显着降低。 。因此，两个通道的平均传热速率随着通道之间壁过热程度的不平等扩大而降低。在平均流量高的条件下，不均匀加热条件下的平均传热系数的劣化是显着的，这需要较大的蒸发传热速率。